Taylor and Calvin began dating earlier this year and Ellie Goulding has already revealed that she played matchmaker by setting them up on a date.
Although singer-songwriter John said he felt "weird" about commenting on "one of the most powerful women in the world right now and one of your best mates", he revealed to Free Radio:"The only thing I can say is that it's nice because he's my friend and he says that she's a laugh and he's happy.
"I haven't hung out with them because I came away from LA when they just started getting together and that's it really. She makes him happy and she's a good laugh, so that's good."
Speaking about his close friendship with Calvin, 'Love Me Again' hitmaker John, added: "We're very good friends now. He's genuinely a lovely, lovely person and it's quite nice when you're out there to have the honesty.
"He's very honest and as a friend he'll sit and tell you how it should be and things like that."
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